If they are roleplaying anything higher than a Matrose (Private), it causes disruptions in the chain of command. How is, say, Obergefreiter (Lance Corporal) [RM]-Watz.Hisname to react when alleged Hauptefreiter (Corporal) Ran.dom.guy issues him an order? It's easier to handle with officers, since they generally have specific commisons, but when you are dealing with NCOs and enlisteds, it gets thorny, and some people roleplay in these ranks.
What you are describing sounds like an unusual and short term situation that wouldn't even last long enough to merit debate.